JP2004289186A - Forming method of insulating film, and manufacturing method of semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a very thin oxynitride film on a silicon substrate surface in almost one process, and to control the oxynitride film so as to be any desired nitrogen concentration in a depth direction to be formed. <P>SOLUTION: There are provided a remote plasma source 26 forming a nitrogen radical and an oxygen radical by using a high frequency plasma, and a processing vessel 21 for holding a substrate to be processed. On the processed substrate an insulating film is formed by a substrate processing unit 100 provided with a gas supplying provision 30 for controlling a supplying ratio of the nitrogen radical and the oxygen radical. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a semiconductor device, and more particularly to a method for manufacturing an ultra-miniaturized high-speed semiconductor device having a high dielectric film.

  In today's ultrahigh-speed semiconductor devices, a gate length of 0.1 μm or less is becoming possible with the progress of the miniaturization process. In general, the operating speed of a semiconductor device increases with miniaturization.However, in such a very miniaturized semiconductor device, the thickness of the gate insulating film is reduced according to a scaling rule as the gate length is reduced by miniaturization. Need to be done.

  However, when the gate length is 0.1 μm or less, the thickness of the gate insulating film must be set to 1 to 2 nm or less when a conventional thermal oxide film is used. In the insulating film, a problem that a tunnel current increases and a gate leakage current increases as a result cannot be avoided.

Conventionally In these circumstances, much larger than that of the dielectric constant of the thermal oxide film, Ya thickness is less of Ta ₂ O ₅ which has a case in terms of SiO ₂ film be actual film thickness for this large It has been proposed to apply a high dielectric material such as Al ₂ O ₃ , ZrO ₂ , HfO ₂ , or ZrSiO ₄ or HfSiO ₄ to a gate insulating film. By using such a high-dielectric material, a gate insulating film having a physical thickness of about 10 nm can be used even in an ultra-high-speed semiconductor device having a gate length of 0.1 μm or less, which is extremely short. Gate leak current can be suppressed.

For example, it is conventionally known that a Ta ₂ O ₅ film can be formed by a CVD method using Ta (OC ₂ H ₅ ) ₅ and O ₂ as a gas phase material. Typically, the CVD process is performed in a vacuum environment at a temperature of about 480 ° C. or higher. The Ta ₂ O ₅ film thus formed is further heat-treated in an oxygen atmosphere, so that oxygen deficiency in the film is eliminated and the film itself is crystallized. The Ta ₂ O ₅ film thus crystallized exhibits a large relative dielectric constant.

  From the viewpoint of improving carrier mobility in the channel region, an extremely thin base oxide film having a thickness of 1 nm or less, preferably 0.8 nm or less is interposed between the high dielectric gate oxide film and the silicon substrate. preferable. The base oxide film needs to be very thin, and if the thickness is large, the effect of using the high dielectric film as the gate insulating film is offset. On the other hand, such a very thin base oxide film needs to uniformly cover the surface of the silicon substrate, and is required not to form defects such as interface states.

  FIG. 1 shows a schematic configuration of a high-speed semiconductor device 10 having a high dielectric gate insulating film.

Referring to FIG. 1, a semiconductor device 10 is formed on a silicon substrate 11, and Ta ₂ O ₅ , Al ₂ O ₃ , ZrO ₂ , and HfO are formed on the silicon substrate 11 via a thin base oxide film 12. ₂ , a high dielectric gate insulating film 13 of ZrSiO ₄ , HfSiO ₄ or the like is formed, and a gate electrode 14 is formed on the high dielectric gate insulating film 13.
JP-A-2002-100267 WO 02/23614 JP 09-148543 A

However, in the semiconductor device 10, in order to exhibit the function of the high dielectric gate insulating film 13 formed on the base oxide film 12, the deposited high dielectric film 13 is crystallized by heat treatment, It is necessary to compensate. When such a heat treatment is performed on the high dielectric film 13, there is a problem that the thickness of the base oxide film 12 increases.
One of the causes of the increase in the thickness of the base oxide film 12 due to the heat treatment is that when the heat treatment is performed, the silicon of the base oxide film layer 12 and the metal of the high dielectric film 13 interdiffuse. It is inferred that a silicate layer was formed. Such a problem of an increase in the film thickness due to the heat treatment of the base oxide film 12 is very serious particularly when the film thickness of the base oxide film 12 is reduced to a thickness of several atomic layers or less, which is desirable as the base oxide film. It becomes a problem.
As a measure to suppress the increase in the thickness of the base oxide film, the semiconductor device 20 shown in FIG. 2 is formed by nitriding the surface of the base oxide film layer to form an oxynitride film. However, in the figure, the parts described above are denoted by the same reference numerals, and description thereof will be omitted.
Referring to FIG. 2, the surface portion of the base oxide film layer 12 is doped with nitrogen (N) in a range where the flatness of the interface between the silicon substrate 11 and the base oxide film 12 is maintained. The oxynitride film 12A is formed to prevent the formation of the silicate layer as described above and increase in the thickness of the base oxide film 12.
However, in the case of the semiconductor device 20, there is a need to newly add a step of nitriding the base oxide film layer 12 and nitriding the oxynitride film 12A, which causes a problem that productivity is reduced. Further, there is a problem that it is very difficult to control the nitrogen concentration in the depth direction of the base oxide film layer 12. In particular, it is known that when nitrogen is concentrated near the interface between the silicon substrate 11 and the base oxide film 12, an interface state is formed, which causes problems such as capture of carriers and formation of a leak current path.

  Accordingly, it is a general object of the present invention to provide a new and useful substrate processing method and substrate apparatus which solve the above-mentioned problems.

  A more specific object of the present invention is to provide a substrate processing method and a substrate processing apparatus capable of forming a very thin, typically 1 to 3 atomic layer oxynitride film on a silicon substrate surface in a single step. To provide.

  Another object of the present invention is to provide a substrate processing method and a substrate processing method capable of controlling an extremely thin, typically 1 to 3 atomic layer oxynitride film on a silicon substrate surface to a desired nitrogen concentration in a formed depth direction. An object of the present invention is to provide a processing device.

The present invention solves the above problems,
As described in claim 1,
A first step of mixing a gas that is nitrogen gas or a nitrogen compound and a gas that is oxygen gas or an oxygen compound to form a mixed gas;
A second step of exciting the mixed gas with high-frequency plasma to form nitrogen radicals and oxygen radicals;
A third step of supplying the nitrogen radicals and the oxygen radicals to the surface of the substrate including silicon,
A method for forming an insulating film, comprising: a fourth step of forming an insulating film containing nitrogen on the surface of the substrate to be processed by the nitrogen radical and the oxygen radical,
The nitrogen radicals and the oxygen radicals are supplied along with a flow of a gas formed to flow along the surface of the substrate to be processed.
As described in claim 2,
The method according to claim 1, wherein the substrate to be processed is a silicon substrate, and the insulating film is an oxynitride film.
As described in claim 3,
The method according to claim 1, wherein the flow of the gas flows from a first side of the substrate to be processed to a second side radially opposed to the first side. 4. ,
As described in claim 4,
The method according to any one of claims 1 to 3, wherein the high-frequency plasma is formed by exciting nitrogen gas and oxygen gas at a frequency of 400 to 500 kHz. Also,
As described in claim 5,
The method of forming an insulating film according to any one of claims 1 to 4, wherein the thickness of the insulating film is 1 nm or less.
As described in claim 6,
The oxygen concentration of the mixed gas is 10 ppm to 600 ppm, and the method of forming an insulating film according to any one of claims 1 to 5,
As described in claim 7,
A first step of mixing a gas that is nitrogen gas or a nitrogen compound and a gas that is oxygen gas or an oxygen compound to form a mixed gas;
A second step of exciting the mixed gas with high-frequency plasma to form nitrogen radicals and oxygen radicals;
A third step of supplying the nitrogen radicals and the oxygen radicals to the surface of the substrate including silicon,
A method for forming an insulating film, comprising: a fourth step of forming an insulating film containing nitrogen on the surface of the substrate to be processed by the nitrogen radical and the oxygen radical,
The high-frequency plasma is formed by exciting a nitrogen gas and an oxygen gas at a frequency of 400 to 500 kHz.
As described in claim 8,
The method according to claim 7, wherein the substrate to be processed is a silicon substrate, and the insulating film is an oxynitride film.
As described in claim 9,
9. The method according to claim 7, wherein the thickness of the insulating film is 1 nm or less.
As described in claim 10,
The method according to any one of claims 7 to 9, wherein the oxygen concentration of the mixed gas is 10 ppm to 600 ppm.
As described in claim 11,
A first step of mixing a gas that is nitrogen gas or a nitrogen compound and a gas that is oxygen gas or an oxygen compound to form a mixed gas;
A second step of exciting the mixed gas with high-frequency plasma to form nitrogen radicals and oxygen radicals;
A third step of supplying the nitrogen radicals and the oxygen radicals to the surface of the substrate including silicon,
A method for manufacturing a semiconductor device, comprising: a fourth step of forming an insulating film containing nitrogen on a surface of a substrate to be processed by using the nitrogen radicals and the oxygen radicals,
The method for manufacturing a semiconductor device, wherein the nitrogen radicals and the oxygen radicals are supplied on a flow of gas formed to flow along the surface of the substrate to be processed,
As described in claim 12,
The method according to claim 11, wherein the substrate to be processed is a silicon substrate, and the insulating film is an oxynitride film.
As described in claim 13,
13. The method of manufacturing a semiconductor device according to claim 11, wherein the flow of the gas flows from a first side of the substrate to be processed to a second side radially opposed to the first side. ,
As described in claim 14,
The method according to any one of claims 11 to 13, wherein the high-frequency plasma is formed by exciting nitrogen gas and oxygen gas at a frequency of 400 to 500 kHz. Also,
As described in claim 15,
The method of manufacturing a semiconductor device according to claim 11, wherein the thickness of the insulating film is 1 nm or less.
As described in claim 16,
The method according to any one of claims 11 to 15, wherein the oxygen concentration of the mixed gas is 10 ppm to 600 ppm.
As described in claim 17,
A first step of mixing a gas that is nitrogen gas or a nitrogen compound and a gas that is oxygen gas or an oxygen compound to form a mixed gas;
A second step of exciting the mixed gas with high-frequency plasma to form nitrogen radicals and oxygen radicals;
A third step of supplying the nitrogen radicals and the oxygen radicals to the surface of the substrate including silicon,
A method for manufacturing a semiconductor device, comprising: a fourth step of forming an insulating film containing nitrogen on the surface of the substrate to be processed by the nitrogen radical and the oxygen radical,
The high-frequency plasma is formed by exciting a nitrogen gas and an oxygen gas at a frequency of 400 to 500 kHz.
As described in claim 18,
18. The method according to claim 17, wherein the substrate to be processed is a silicon substrate, and the insulating film is an oxynitride film.
As described in claim 19,
19. The method according to claim 17, wherein the thickness of the insulating film is 1 nm or less.
As described in claim 20,
20. The method according to claim 17, wherein the mixed gas has an oxygen concentration of 10 ppm to 600 ppm.
[Action]
According to the present invention, a very thin oxynitride film can be formed in a single step using nitrogen radicals and oxygen radicals excited by high-frequency plasma, and an oxynitride film is formed by nitriding an oxide film. The number of steps can be reduced as compared with the case of forming, and the productivity can be improved. Further, according to the present invention, in the oxynitride film forming step, the amount of oxygen radicals added to the supplied nitrogen radicals can be controlled during the formation of the oxynitride film. As a result, the nitrogen concentration in the formed oxynitride film can be controlled to a desired profile in the depth direction of the formed oxynitride film.

  In this case, since the dielectric constant of the oxynitride film is larger than that of the conventionally used silicon oxide film, the equivalent oxide thickness of the thermal oxide film can be reduced.

  According to the present invention, it is possible to form a very thin, typically 1 to 3 atomic layer oxynitride film on a silicon substrate surface in a single step.

  Further, it is possible to control the oxynitride film to a desired nitrogen concentration in a depth direction in which the oxynitride film is formed.

  Next, an embodiment of the invention will be described.

  FIG. 3 shows a schematic configuration of a substrate processing apparatus 100 for forming an oxynitride film on the silicon substrate 11 of FIG. 2 according to the first embodiment of the present invention.

Referring to FIG. 3, the substrate processing apparatus 100 stores a substrate holding table 22 provided with a heater 22 </ b> A and provided to be vertically movable between a process position and a substrate loading / unloading position. The apparatus includes a processing vessel 21 defining a process space 21B, and the substrate holding table 22 is rotated by a driving mechanism 22C. The inner wall surface of the processing vessel 21 is covered with an inner liner 21G made of quartz glass, whereby metal contamination of the substrate to be processed from the exposed metal surface is reduced to a level of 1 × 10 ¹⁰ atoms / cm ² or less. Restrained.

  A magnetic seal 28 is formed at the joint between the substrate holding table 22 and the driving mechanism 22C. The magnetic seal 28 connects the magnetic sealing chamber 22B held in a vacuum environment and the driving mechanism 22C formed in the atmospheric environment. Are separated. Since the magnetic seal 28 is a liquid, the substrate holder 22 is rotatably held.

  In the illustrated state, the substrate holding table 22 is at the process position, and a loading / unloading chamber 21C for loading / unloading the substrate to be processed is formed below. The processing container 21 is connected to the substrate transfer unit 27 via a gate valve 27A. When the substrate holding table 22 is lowered into and out of 21C during loading / unloading, the substrate transfer unit 27 is connected via the gate valve 27A. Then, the substrate W to be processed is transferred onto the substrate holder 22, and the processed substrate W is transferred from the substrate holder 22 to the substrate transfer unit 27.

In the substrate processing apparatus 100 of FIG. 3, an exhaust port 21A is formed in a portion of the processing container 21 near the gate valve 27A, and a turbo molecular pump 23B is connected to the exhaust port 21A via a valve 23A. . The turbo molecular pump 23B is further connected with a pump 24 configured by combining a dry pump and a mechanical booster pump via a valve 23C. By driving the turbo molecular pump 23B and the dry pump 24, the turbo molecular pump 23B The pressure in the process space 21B can be reduced to 1.33 × 10 ⁻¹ to 1.33 × 10 ⁻⁴ Pa (10 ⁻³ to 10 ⁻⁶ Torr), while the exhaust port 21A is connected to the valve 24A and The process space is also directly connected to the pump 24 via the APC 24B, and by opening the valve 24A, the process space is increased by the pump 24 to a pressure of 1.33 to 13.3 kPa (0.01 to 100 Torr). The pressure is reduced.

  The processing vessel 21 is provided with a remote plasma source 26 on the side of the substrate W facing the exhaust port 21A. The remote plasma source 26 is further provided with a gas for supplying nitrogen and oxygen. The supply device 30 is connected. In the gas supply device 30, a slight amount of oxygen is mixed with the supplied nitrogen by a method described later with reference to FIGS. 9 to 13 to adjust the mixture to a predetermined mixing ratio (about 10 ppm to 600 ppm in oxygen concentration). . A mixture of nitrogen and oxygen adjusted by the above-described method is supplied to the remote plasma source 26 together with an inert gas such as Ar, and the mixture is activated by plasma. Is formed. Thus, by adjusting the mixture ratio of nitrogen and oxygen supplied to the remote plasma source 26, it is possible to adjust the ratio of nitrogen radicals to oxygen radicals generated by the remote plasma source 26, As a result, an oxynitride film adjusted to a desired nitrogen concentration can be formed on the target substrate W.

  In the substrate processing apparatus 100 of FIG. 3, a purge line 21c for purging the loading / unloading chamber 21C with nitrogen gas is further provided, and a purge line 22b for purging the magnetic seal chamber 22B with nitrogen gas and an exhaust line 22c thereof are provided. Is provided. More specifically, a turbo-molecular pump 29B is connected to the exhaust line 22c via a valve 29A, and the turbo-molecular pump 29B is connected to the pump 24 via a valve 29C. Further, the exhaust line 22c is directly connected to the pump 24 via a valve 29D, so that the magnetic seal chamber 22B can be maintained at various pressures.

The loading / unloading chamber 21C is exhausted by a pump 24 via a valve 24C or exhausted by a turbo molecular pump 23B via a valve 23D. In order to avoid the occurrence of contamination in the process space 21B, the loading / unloading chamber 21C is maintained at a lower pressure than the process space 21B, and the magnetic sealing chamber 22B is differentially evacuated so that the loading / unloading is performed. The pressure is kept lower than that of the discharge chamber 21C.
Next, the configuration of the remote plasma source 26 provided in the substrate processing apparatus 100 will be described.

  FIG. 4 shows a configuration of the remote plasma source 26 used in the substrate processing apparatus 40 of FIG.

  Referring to FIG. 4, the remote plasma source 26 includes a block 26A, typically made of aluminum, in which a gas circulation passage 26a and a gas inlet 26b and a gas outlet 26c communicating therewith are formed. A ferrite core 26B is formed in a part of 26A.

  The inner surface of the gas circulation passage 26a, the gas inlet 26b, and the gas outlet 26c is coated with a fluororesin coating 26d, and the coil wound around the ferrite core 26B is supplied with a high frequency having a frequency of 400 kHz. Plasma 26C is formed in passage 26a.

With the excitation of the plasma 26C, nitrogen radicals, oxygen radicals, nitrogen ions and oxygen ions are formed in the gas circulation passage 26a, but the nitrogen ions and oxygen ions disappear when circulating through the circulation passage 26a. From the gas outlet 26c, nitrogen radicals N ₂ * and oxygen radicals O ₂ * are mainly released. Further, in the configuration of FIG. 4, by providing an ion filter 26e grounded to the gas outlet 26c, charged particles including nitrogen ions are removed, and only nitrogen radicals and oxygen radicals are supplied to the processing space 21B. . Further, even when the ion filter 26e is not grounded, the structure of the ion filter 26e functions as a diffusion plate, so that charged particles including nitrogen ions can be sufficiently removed.

  FIG. 5 shows the relationship between the number of ions formed by the remote plasma source 26 in FIG. 4 and the electron energy in comparison with the case of the microwave plasma source.

Referring to FIG. 5, when plasma is excited by microwaves, ionization of nitrogen molecules and oxygen molecules is promoted, and a large amount of nitrogen ions and oxygen ions are formed. On the other hand, when the plasma is excited by a high frequency of 500 kHz or less, the number of formed nitrogen ions and oxygen ions is greatly reduced. In the case of performing plasma processing by microwaves, as shown in FIG. 6, a high vacuum of 1.33 × 10 ^{−3 to} 1.33 × 10 ⁻⁶ Pa (10 ⁻¹ to 10 ⁻⁴ Torr) is required. However, the high-frequency plasma processing can be performed at a relatively high pressure of 13.3 to 13.3 kPa (0.1 to 100 Torr).

  Next, FIG. 7 shows a comparison of ionization energy conversion efficiency, dischargeable pressure range, plasma power consumption, and process gas flow rate between the case where plasma is excited by microwaves and the case where plasma is excited by high frequencies. .

Referring to FIG. 7, the ionization energy conversion efficiency is about 1 × 10 ^{−2 in} the case of microwave excitation, while it is reduced to about 1 × 10 ^{−7 in} the case of RF excitation, and The dischargeable pressure is about 0.1 mTorr to 0.1 Torr (133 mPa to 13.3 Pa) in the case of microwave excitation, whereas 0.1 to 100 Torr (13.3 Pa to 13.3 kPa) in the case of RF excitation. ). Accordingly, the plasma power consumption is larger in the case of RF excitation than in the case of microwave excitation, and the process gas flow rate is much larger in the case of RF excitation than in the case of microwave excitation.

  In the substrate processing apparatus shown in FIG. 3, the oxynitride film is formed not by nitrogen ions and oxygen ions but by nitrogen radicals and oxygen radicals. Therefore, it is preferable that the number of excited nitrogen ions and oxygen ions is small. Also, from the viewpoint of minimizing damage to the substrate to be processed, it is preferable that the number of excited nitrogen ions and oxygen ions is small. Further, in the substrate processing apparatus of FIG. 3, the number of excited nitrogen radicals and oxygen radicals is small, which is suitable for forming an extremely thin oxynitride film under the high-dielectric gate insulating film.

  FIGS. 8A and 8B are a side view and a plan view showing a case where an oxynitride film is formed on a substrate W to be processed using the substrate processing apparatus 100 of FIG. However, in the figure, the parts described above are denoted by the same reference numerals, and description thereof will be omitted.

The procedure for actually forming the oxynitride film on the target substrate W is as follows.
First, Ar gas, nitrogen gas and oxygen adjusted to a predetermined mixing ratio as described above are supplied from the gas supply device 30 to the remote plasma radical source 26, and high frequency excitation of the plasma is performed at a frequency of several hundred kHz. As a result, nitrogen radicals and oxygen radicals having a predetermined mixing ratio are formed. The formed nitrogen radicals and oxygen radicals flow along the surface of the target substrate W, and are exhausted through the exhaust port 21A and the pump 24. As a result, the process space 21B is set to a process pressure in a range of 6.65 Pa to 1.33 kPa (0.05 to 10 Torr), which is suitable for radical oxynitriding of the substrate W. In this way, when the nitrogen radicals and the oxygen radicals flow along the surface of the substrate to be processed W, the surface of the substrate to be processed W which is rotating is very thin, typically 1 to 3 atoms. An oxynitride layer is formed.

In the oxynitride film forming process of FIGS. 8A and 8B, the following purging process can be performed prior to the oxynitride film formation. In the purge step, the pressure in the processing space 21B is reduced to a pressure of 1.33 × 10 ⁻¹ to 1.33 × 10 ⁻⁴ Pa by opening the valves 23A and 23C and closing the valve 24A. However, in the subsequent oxynitride film forming step, the valves 23A and 23C are closed, and the turbo molecular pump 23B is not included in the exhaust path of the process space 21B.

  By adding the purging step, it is possible to purge oxygen and moisture remaining in the processing space 21B.

  In addition, as can be seen from the plan view of FIG. 8B, the turbo molecular pump 23B is arranged so as to protrude to the side of the processing container 21, avoiding the substrate transfer unit 27. In this case, as shown in the following FIGS. 9A and 9B, the arrangement of the turbo molecular pump 23B can be changed.

  9A and 9B are a side view and a plan view, respectively, showing the configuration of the substrate processing apparatus 40. However, in FIGS. 9A and 9B, the same reference numerals are given to the parts described above, and the description will be omitted.

  9A and 9B, in the substrate processing apparatus 40, the turbo molecular pump 23B is disposed outside the processing container 21, that is, on the side opposite to the substrate transfer unit 27 as shown in FIG. Accordingly, an exhaust port 21E cooperating with the turbo molecular pump 23B is formed in the processing container 21 on the side opposite to the substrate transfer chamber.

  The turbo-molecular pump 23B is coupled via a valve 23A in a direction perpendicular to the lower part of the processing vessel 21, that is, in a direction in which an intake port and an exhaust port are vertically arranged. Is connected to the exhaust line from the exhaust port 21A of the processing container 21 to the pump 24 via the valve 24A after the valve 24A.

  In the substrate processing apparatus 40, since the turbo-molecular pump 23B is disposed below the processing container 21, the space of the substrate processing apparatus can be reduced as compared with the substrate processing apparatus 100 described above.

The procedure for actually forming the oxynitride film on the target substrate W is as follows.
First, Ar gas, nitrogen gas and oxygen adjusted to a predetermined mixing ratio as described above are supplied from the gas supply device 30 to the remote plasma radical source 26, and high frequency excitation of the plasma is performed at a frequency of several hundred kHz. As a result, nitrogen radicals and oxygen radicals having a predetermined mixing ratio are formed. The formed nitrogen radicals and oxygen radicals flow along the surface of the target substrate W, and are exhausted through the exhaust port 21A and the pump 24. As a result, the process space 21B is set to a process pressure in a range of 6.65 Pa to 1.33 kPa (0.05 to 10 Torr), which is suitable for radical oxynitriding of the substrate W. In this way, when the nitrogen radicals and the oxygen radicals flow along the surface of the substrate to be processed W, the surface of the substrate to be processed W which is rotating is very thin, typically 1 to 3 atoms. An oxynitride layer is formed.

In the oxynitride film forming process of FIGS. 9A and 9B, a purge process described below can be performed prior to the formation of the oxynitride film. In the purge step, the pressure in the processing space 21B is reduced to a pressure of 1.33 × 10 ⁻¹ to 1.33 × 10 ⁻⁴ Pa by opening the valves 23A and 23C and closing the valve 24A. However, in the subsequent oxynitriding process, the valves 23A and 23C are closed, and the turbo molecular pump 23B is not included in the exhaust path of the process space 21B.

  By adding the purging step, it is possible to purge oxygen and moisture remaining in the processing space 21B.

  Next, a configuration diagram of the gas supply device 30 that supplies nitrogen and oxygen to the remote plasma source 26 is shown.

  Referring to FIG. 10, the gas supply device 30 includes a nitrogen supply line 31 including a nitrogen supply valve 31A, an oxygen supply line 32 including an oxygen supply valve 32A, a mixing tank 30A, and a mixture supply including a mixture supply valve 33A. It is composed of a line 33. By opening the nitrogen introduction valve 31A in the nitrogen introduction line 31, nitrogen is introduced into the mixing tank 30A. When mixing oxygen in the mixing tank 30A, the oxygen introduction valve 32A is opened for a short time while nitrogen is being supplied, and a trace amount of oxygen is mixed into the mixing tank through the oxygen introduction line 32. The concentration of oxygen to be mixed is adjusted by the opening time of the oxygen introduction valve 32A. The nitrogen and oxygen mixed in the mixing tank 30A are supplied from the mixed gas supply line 33 to the remote plasma source 26 by opening the mixed gas supply valve 33A.

  As described above, by adjusting the concentration of oxygen to nitrogen in the mixed gas supplied to the remote plasma source 26, it is possible to adjust the ratio of nitrogen radicals to oxygen radicals to be formed. It is possible to form a very thin, typically 1 to 3 atomic layer oxynitride film with a desired nitrogen concentration in 21.

  In addition, compared to the case where the oxynitride film is formed by nitriding the surface after forming the oxide film, the number of steps can be reduced by one because the oxynitride film can be formed in one step. Productivity can be improved.

  Next, a method for controlling the nitrogen concentration of the formed oxynitride film will be specifically described.

  FIG. 11 is a timing chart showing the timing of opening and closing the nitrogen gas supply valve 31A and the oxygen gas supply valve 32A on the horizontal axis with the passage of time.

  Referring to FIG. 11, the nitrogen gas 31A is kept open while supplying a mixed gas of nitrogen and oxygen. The oxygen supply valve 32A is repeatedly opened and closed for a short period of time and then opened and closed again for a short period of time after a lapse of a predetermined time, thereby adding predetermined oxygen to nitrogen to adjust the oxygen concentration to a desired value. Assuming that the opening time of the oxygen supply valve 32A at this time is t1 and the time from when the oxygen supply valve 32A is opened to when it is opened again is S1, the values of t1 and S1 are adjusted to mix with nitrogen. Oxygen concentration can be adjusted. As a result, the ratio of nitrogen radicals to oxygen radicals generated in the remote plasma source 26 can be adjusted, and the nitrogen concentration of the oxynitride film formed on the substrate W can be adjusted to a desired value. It becomes possible.

  In this case, since the oxidation reaction rate is higher than that of nitriding, the concentration of oxygen added to nitrogen can be controlled to about 10 ppm to 600 ppm, and the nitrogen concentration of the oxynitride film can be controlled to about 10 to 40%.

  The conditions for forming the oxynitride film in this case include, for example, a pressure of the processing container 21 of 6.65 Pa to 1.33 kPa (0.05 to 10 Torr), an Ar gas flow of 0.7 to 2 slm, and a nitrogen flow of 0.05 to 0. 9 slm, an oxygen flow rate of 0 to 0.1 slm, an oxygen concentration of 10 to 600 ppm in a mixture of nitrogen and oxygen, or an oxygen concentration of 10 to 300 ppm in a mixture of nitrogen, Ar and oxygen, and a substrate temperature of 400 to 700 ° C. Then, the nitrogen concentration in the formed oxynitride film becomes about 10 to 40%.

  Next, FIG. 12 shows a timing chart in which the time lapse of the nitrogen supply valve 31A and the oxygen supply valve 32A according to the second embodiment of the present invention is plotted on the horizontal axis.

  Referring to FIG. 12, as compared with the case of the first embodiment in FIG. 11, S1 is the same, but the time t1 during which the oxygen supply valve 32A is open becomes t2 and t1 in the present example. It is shorter than. This reduces the amount of oxygen mixed. As a result, the amount of oxygen radicals generated in the remote plasma source 26 is reduced, and an oxidation reaction when forming an oxynitride film on the substrate W to be processed is suppressed. As a result, in the step of forming the oxynitride film, the nitridation is advanced compared to the case of the first embodiment, and the nitrogen concentration in the formed oxynitride film can be increased.

  Next, FIG. 13 shows a timing chart in which the time lapse of the nitrogen supply valve 31A and the oxygen supply valve 32A according to the third embodiment of the present invention is plotted on the horizontal axis.

  Referring to FIG. 13, the time t1 is the same as in the case of the first embodiment in FIG. 11, but the time S1 from the time when the oxygen supply valve 32A is opened to the time when the oxygen supply valve 32A is opened again is the same as in the present embodiment. In the case of, S2 is longer than S1. This reduces the amount of oxygen mixed. As a result, the amount of oxygen radicals generated in the remote plasma source 26 is reduced, and an oxidation reaction when forming an oxynitride film on the substrate W to be processed is suppressed. As a result, in the step of forming the oxynitride film, the nitridation is advanced compared to the case of the first embodiment, and the nitrogen concentration in the formed oxynitride film can be increased.

Next, FIG. 14 shows a timing chart in which the time lapse of the nitrogen supply valve 31A and the oxygen supply valve 32A according to the fourth embodiment of the present invention is plotted on the horizontal axis.

  Referring to FIG. 14, in the first half of the oxynitridation process indicated by A in the figure immediately after the start of the supply, compared to the case of Example 1 in FIG. Identical. In the latter half of the oxynitriding step indicated by B in the figure, t1 is changed to t2, the open time of the oxygen supply valve 32A is shortened, and the amount of oxygen mixed is reduced. For this reason, as described in the description of the second embodiment, in the step of forming the oxynitride film, the nitridation is advanced compared to the case of the first embodiment, and the nitrogen concentration in the formed oxynitride film is increased. It is possible to do. In this case, the nitrogen concentration is low in the first half of the oxynitride film formation step, and is high in the second half of the oxynitride formation step.

  In an actual semiconductor device, when considering the above-described oxynitride film formation process, considering the device characteristics, the portion close to the Si substrate, that is, the interface between the silicon and the oxynitride film becomes flat in the first half of the oxynitride process. A low nitrogen concentration is required for easy formation. In the oxynitride film to be formed, in a portion close to the high dielectric film formed on the oxynitride film, that is, in a portion formed in the latter half of the oxynitridation step, mutual diffusion of metal and silicon is prevented. Therefore, a higher nitrogen concentration is better. In this embodiment, it is possible to form an oxynitride film adjusted to a nitrogen concentration that satisfies the above-mentioned requirements for device characteristics in the depth direction of the oxynitride film.

Next, FIG. 15 shows a timing chart in which the time lapse of the nitrogen supply valve 31A and the oxygen supply valve 32A according to the fifth embodiment of the present invention is plotted on the horizontal axis.

  Referring to FIG. 15, compared to the case of Example 1 in FIG. 11, immediately after the start of the supply, the first half of the oxynitridation process represented by A in FIG. Is the same as In the latter half of the oxynitriding step indicated by B in the figure, S1 is changed to S2, the time from opening the oxygen supply valve 32A to opening it again is increased, and the mixed amount of oxygen increases. I have. For this reason, in the latter half of the supply, as described in the description of the third embodiment, in the step of forming the oxynitride film, the nitridation is advanced as compared with the case of the first embodiment. It is possible to increase the nitrogen concentration. In this case, the nitrogen concentration is low in the first half of the oxynitriding step, and the nitrogen concentration is high in the second half of the oxynitriding step.

  In an actual semiconductor device, when considering the above-described oxynitride film formation process, considering the device characteristics, the portion close to the Si substrate, that is, the interface between the silicon and the oxynitride film becomes flat in the first half of the oxynitride process. A low nitrogen concentration is required for easy formation. In the oxynitride film to be formed, in a portion close to the high dielectric film formed on the oxynitride film, that is, in a portion formed in the latter half of the oxynitridation step, mutual diffusion of metal and silicon is prevented. Therefore, a higher nitrogen concentration is better. In this embodiment, in the depth direction of the oxynitride film, it is possible to form an oxynitride film adjusted to a nitrogen concentration that satisfies the above-described requirements for device characteristics.

  Further, the method of adding oxygen radicals to nitrogen radicals is not limited to the method of adding oxygen to nitrogen gas, but can be a combination of a gas containing nitrogen and oxygen. For example, a method of adding NO gas to nitrogen gas or adding oxygen to NO gas is possible.

  As described above, the present invention has been described with reference to the preferred embodiments. However, the present invention is not limited to the above-described specific embodiments, and various modifications and changes can be made within the scope of the claims.

  According to the present invention, it is possible to form a very thin, typically 1 to 3 atomic layer oxynitride film on a silicon substrate surface in a single step.

  Further, it is possible to control the oxynitride film to a desired nitrogen concentration in a depth direction in which the oxynitride film is formed.

FIG. 3 is a diagram showing a configuration of a semiconductor device having a high dielectric gate insulating film and a base oxide film. FIG. 3 is a diagram showing a configuration of a semiconductor device having a high dielectric gate insulating film, a base oxide film, and an oxynitride film. FIG. 1 is a diagram illustrating a configuration of a substrate processing apparatus according to a first embodiment of the present invention. FIG. 4 is a diagram illustrating a configuration of a remote plasma source used in the substrate processing apparatus of FIG. 3. FIG. 4 is a diagram comparing characteristics of RF remote plasma and microwave plasma. FIG. 3 is a diagram comparing characteristics regarding discharge of RF remote plasma and microwave plasma. This is a comparison between a case where plasma is excited by a microwave and a case where plasma is excited by a high frequency. (A), (B) is a diagram showing the formation of an oxynitride film by the substrate processing apparatus according to the present invention. (A), (B) is another figure which shows formation of an oxynitride film by the substrate processing apparatus by this invention. It is a figure showing composition of a gas supply device. FIG. 2 is a diagram illustrating a method of mixing nitrogen and oxygen used in Example 1 of the present invention. FIG. 6 is a diagram showing a mixing system of nitrogen and oxygen used in a second embodiment of the present invention. FIG. 11 is a diagram showing a mixing system of nitrogen and oxygen used in a third embodiment of the present invention. FIG. 11 is a diagram illustrating a method of mixing nitrogen and oxygen used in a fourth embodiment of the present invention. FIG. 14 is a diagram showing a mixing system of nitrogen and oxygen used in a fifth embodiment of the present invention.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 10, 20 Semiconductor device 11 Silicon substrate 12 Base oxide film 12A Oxynitride film 13 High dielectric film 14 Gate electrode 40, 100 Substrate processing apparatus 21 Processing container 21A Exhaust port 21E Exhaust port 21B Process space 21C Substrate loading / unloading chamber 21c, 22b, 22c Purge line 21G Quartz liner 22 Substrate holder 22A Heater 22B Magnetic seal tank 22C Substrate rotation mechanism 23A, 23C, 23D, 24A, 24B, 24C, 29A, 29D Valve 23B, 29B Turbo molecular pump 24 Pump 26 Remote plasma source 26A Block 26B Ferrite core 26C Plasma 26a Gas circulation passage 26b Gas inlet 26c Gas outlet 26d Coating 26e Ion filter 27 Substrate transfer unit 27A Gate valve 30 Gas supply device 30A Mixing tank 31 Nitrogen supply line 32 Oxygen supply line 33 Mixture supply line 31A, 32A, 33A Valve

Claims (20)

A first step of mixing a gas that is nitrogen gas or a nitrogen compound and a gas that is oxygen gas or an oxygen compound to form a mixed gas;
A second step of exciting the mixed gas with high-frequency plasma to form nitrogen radicals and oxygen radicals;
A third step of supplying the nitrogen radicals and the oxygen radicals to the surface of the substrate including silicon,
A method for forming an insulating film, comprising: a fourth step of forming an insulating film containing nitrogen on the surface of the substrate to be processed by the nitrogen radical and the oxygen radical,
The method for forming an insulating film, wherein the nitrogen radicals and the oxygen radicals are supplied along with a flow of a gas formed to flow along a surface of the substrate to be processed.   2. The method according to claim 1, wherein the substrate to be processed is a silicon substrate, and the insulating film is an oxynitride film.   3. The method according to claim 1, wherein the flow of the gas flows from a first side of the substrate to be processed to a second side radially opposed to the first side. 4.   4. The method of claim 1, wherein the high-frequency plasma is formed by exciting a nitrogen gas and an oxygen gas at a frequency of 400 to 500 kHz. 5.   The method for forming an insulating film according to claim 1, wherein a thickness of the insulating film is 1 nm or less.   The method for forming an insulating film according to any one of claims 1 to 5, wherein the oxygen concentration of the mixed gas is 10 ppm to 600 ppm. A first step of mixing a gas that is nitrogen gas or a nitrogen compound and a gas that is oxygen gas or an oxygen compound to form a mixed gas;
A second step of exciting the mixed gas with high-frequency plasma to form nitrogen radicals and oxygen radicals;
A third step of supplying the nitrogen radicals and the oxygen radicals to the surface of the substrate including silicon,
A method for forming an insulating film, comprising: a fourth step of forming an insulating film containing nitrogen on the surface of the substrate to be processed by the nitrogen radical and the oxygen radical,
The method for forming an insulating film, wherein the high-frequency plasma is formed by exciting a nitrogen gas and an oxygen gas at a frequency of 400 to 500 kHz.   8. The method according to claim 7, wherein the substrate to be processed is a silicon substrate, and the insulating film is an oxynitride film.   9. The method according to claim 7, wherein the thickness of the insulating film is 1 nm or less.   The method for forming an insulating film according to any one of claims 7 to 9, wherein the oxygen concentration of the mixed gas is 10 ppm to 600 ppm. A first step of mixing a gas that is nitrogen gas or a nitrogen compound and a gas that is oxygen gas or an oxygen compound to form a mixed gas;
A second step of exciting the mixed gas with high-frequency plasma to form nitrogen radicals and oxygen radicals;
A third step of supplying the nitrogen radicals and the oxygen radicals to the surface of the substrate including silicon,
A method for manufacturing a semiconductor device, comprising: a fourth step of forming an insulating film containing nitrogen on a surface of a substrate to be processed by using the nitrogen radicals and the oxygen radicals,
The method of manufacturing a semiconductor device, wherein the nitrogen radicals and the oxygen radicals are supplied along with a flow of a gas formed to flow along a surface of the substrate to be processed.   The method according to claim 11, wherein the substrate to be processed is a silicon substrate, and the insulating film is an oxynitride film.   13. The method according to claim 11, wherein the flow of the gas flows from a first side of the substrate to be processed to a second side radially opposed to the first side.   14. The method of manufacturing a semiconductor device according to claim 11, wherein the high-frequency plasma is formed by exciting nitrogen gas and oxygen gas at a frequency of 400 to 500 kHz.   15. The method according to claim 11, wherein the thickness of the insulating film is 1 nm or less.   The method according to claim 11, wherein an oxygen concentration of the mixed gas is 10 ppm to 600 ppm. A first step of mixing a gas that is nitrogen gas or a nitrogen compound and a gas that is oxygen gas or an oxygen compound to form a mixed gas;
A second step of exciting the mixed gas with high-frequency plasma to form nitrogen radicals and oxygen radicals;
A third step of supplying the nitrogen radicals and the oxygen radicals to the surface of the substrate including silicon,
A method for manufacturing a semiconductor device, comprising: a fourth step of forming an insulating film containing nitrogen on a surface of a substrate to be processed by using the nitrogen radicals and the oxygen radicals,
The method for manufacturing a semiconductor device, wherein the high-frequency plasma is formed by exciting nitrogen gas and oxygen gas at a frequency of 400 to 500 kHz.   The method according to claim 17, wherein the substrate to be processed is a silicon substrate, and the insulating film is an oxynitride film.   19. The method according to claim 17, wherein the thickness of the insulating film is 1 nm or less.   20. The method of manufacturing a semiconductor device according to claim 17, wherein an oxygen concentration of the mixed gas is 10 ppm to 600 ppm.

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